(1) Field of the Invention
The present invention generally relates to the control of the flow of water to torpedo tubes. More particularly the invention provides a new tombstone and the use of disk valves to control the flow of seawater to the torpedo tubes.
(2) Description of the Prior Art
U.S. Naval Submarines are typically equipped with either four or eight torpedo tubes. These torpedo tubes are normally divided evenly into a port and starboard bank of tubes that operate independently of each other.
In operation seawater is initially drawn from outside the hull, through a water cylinder, and into a pump inlet. The inlet's pump is typically either an air powered turbine or a ram pump. The seawater passes through the pump and discharges into a large tank, named the lower impulse tank. The water then exits from the lower impulse tank through a water passage aperture into a smaller tank mounted on top of the lower impulse tank. This smaller tank is referred to as either an upper impulse tank or a tombstone. In this application it is primarily referred to as a tombstone.
The tombstone is a rectangular tank with apertures bored on two opposing sides for each torpedo tube. Each torpedo tube is inserted through a pair of opposed apertures in the tombstone and then welded to the tombstone. Each bank of torpedo tubes share a common tombstone. Rectangular slots are machined into each of the torpedo tubes circumferential walls within the volume bound by the tombstone's walls. These slots allow for the flow of water from the tombstone into the torpedo tube to provide an impulse to eject a vehicle housed within the torpedo tube.
An isolation valve isolates the interior of each torpedo tube from the tombstone allowing the torpedo tube to be free of seawater. To prevent simultaneous weapon ejection, a launch control system allows only one isolation valve to be open at a time. Past U.S. Submarines have always used a tube enclosed slide valve. A slide valve is comprised of a cylinder, gaskets, and actuators. The cylinder, which is slightly smaller than the torpedo tube, is inserted into the aft end of the torpedo tube. The slide valve is positioned to cover the slots that have been machined into the tube. On both ends of the cylinder are gaskets that prevent sea water from seeping between the torpedo tube inner diameter and the cylinder outer diameter. Actuators are mounted on the tube outer diameter to provide power to the cylinder to expose the slots.
There are disadvantages to the use of a slide valve on a submarine. One is that in order to maintain an adequate seal between the slide valve cylinder and the torpedo tube, tolerances of .+-.0.005" are required on the torpedo tube inner diameter and the cylinder outer diameter. This machining operation is performed after the torpedo tube is welded into the submarine. The setup time and portable boring bar operation required to perform this operation in the submarine is both complex and time consuming.
Another disadvantage is that contaminated water flowing through the launch system is known to damage the slide valve gaskets. The water may contain sand, flakes of rust, dirt, paint chips and other foreign matter. These items are often entrapped between the slide valve gaskets and tube as the cylinder slides fore and aft. Cuts in the gasket often occur on the bottom of the tube from particles that settle when the launch system is not in use. Gaskets are frequently replaced due to cuts and excessive wearing. This is a time consuming process.
Arranging the actuators on the torpedo tube has often been a problem. The actuators are mounted on the torpedo tube outside diameter either forward or aft of the tombstone. Mounting aft of the tombstone extends the torpedo tube into the torpedo room. Mounting the actuators forward of the tombstone can result in an interference with the pressure hull.
A goal of any launch system is to reduce the level of noise generated from the flow of water through the system. Known methods to lower this level are to reduce the water velocity through the system and eliminate obstructions. The flow slots in the torpedo tube have been identified as a large contributor since they are an obstruction at a location of accelerating and turning flow. Numerous studies of this region have been conducted in an attempt to optimize the slot geometry to reduce the noise. There is general agreement that if the slots could be eliminated or increased in size then the noise generated would be reduced. Unfortunately, with the current ship designs, the slots cannot be eliminated since the remaining ligaments are a structural element of the tombstone and guide the slide valve cylinder.